Photograph of a hard-start capacitor suitable for an air conditioner compressor motor or heat pump compressorCauses of Hard-Starting Electric Motors
Hard Starting Air Conditioning / Heat Pump Compressor Motor & Other Electric Motors

  • POST a QUESTION or READ FAQs about installing a hard-start capacitor to get an air conditioner motor, fan motor, or other electric motor running.

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Hard-starting electric motor diagnosis & repair:

What causes hard-starting compressor motors, fan motors, or other electric motors?

Understanding why an electric motor is having trouble starting or why it won't keep running is an important diagnostic step in keeping an electric motor or air conditioner, heat pump, well pump or other motor working properly. Understanding why a motor is hard starting also tells us if it makes sense to install a hard-start capacitor on the equipment.

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Causes of Hard-Starting Air Conditioners, Refrigerators, Freezers, and other Electric Motors

A compressor or other motor may have trouble starting for any of a variety of reasons such as:

Electric motor starting capacitor (C) Daniel Friedman

Starting capacitors or electric motor starting capacitors (or motor start boosters) are often present on large single phase air conditioning compressors, as found on home air conditioning units, or on occasion on blower motors or even fan motors.

Electric motor starting capacitors are only very rarely present on small refrigeration compressors, such as those in refrigerators, and as far as we know, never present on 3-phase power systems.

Another common reason for a CS or CSCR motor to fail to start is a bad centrifugal switch. If the switch contacts are dirty, the motor can fail to start. If the switch freezes closed, the start capacitor will overheat. - P.S.M. 10 Jan 2015

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Continue reading at HOW a STARTING CAPACITOR WORKS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

or see ELECTRIC MOTOR DIAGNOSTIC GUIDE for help in testing a bad-behaving electric motor or an electric motor that won't start

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CAUSES of HARD STARTING ELECTRIC MOTORS at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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